This proposal plans to develop a silicon nitride ceramic for total joint prostheses that would articulate against a metal (Cobalt-Chromium, Co-Cr) component. This is propose in an attempt to eliminate the polyethylene- metal wear couples currently in us due to concerns of polyethylene particle induced osteolysis. In an alternate approach to eliminating PE wear debris and lowering the risk of brittle failure, a metal/ceramic couple is proposed where the acetabular liner (for a total hip replacement) is made from a silicon nitride-based ceramic for articulating against a conventional Co-Cr head. Experience with silicon nitride ceramics in other fields points to the potential for superior wear resistance in biomedical applications. Phase I will assess the mechanical properties and demonstrate reduced wear rates against Co-Cr via hip simulator tests. Phase II will include extended wear tests along with design and manufacturing process optimization. PROPOSED COMMERCIAL APPLICATION: The novel combination of an advanced ceramic liner articulating against Co-Cr heads will lead to negligible ware debris and osteolysis mediated implant failures. The proposed materials will find applications in hips, knees and others articulating joints.